Environmental Trends in Air Quality, Pre-1970

The Pacific Research Institute has launched Environmental Trends, a website for the “unconventional environmentalist.” The site is full of useful facts, articles, and charts, including regular contributions from PERC research fellow Holly Fretwell and board member Steven Hayward.

Most reports on air quality trends typically begin with 1970, with the passage of the first Clean Air Act and the beginning of systematic monitoring of emissions and ambient levels of air pollution. Data from early monitors and evidence from air quality models, however, show that many forms of air pollution started to decline—in some cases rapidly—before the Clean Air Act of 1970.

For sulfur dioxide, data from 21 urban monitors show that the average ambient level fell approximately 40 percent between 1962 and 1964 (as shown above). This set the stage for progress after the Clean Air Act; the national average dropped 66 percent since then. Local data for New York City show that ambient sulfur dioxide fell by almost 50 percent between 1964 and 1970, as shown in Figure 2. Fragmentary data also show that carbon dioxide levels were falling in the mid-1960s.